The Organic Light Emitting Display (OLED) possesses many outstanding properties of self-illumination, low driving voltage, high luminescence efficiency, short response time, high clarity and contrast, near 180° view angle, wide range of working temperature, applicability of flexible display and large scale full color display. The OLED is considered as the most potential display device.
The OLED can be categorized into two major types according to the driving methods, which are the Passive Matrix OLED (PMOLED) and the Active Matrix OLED (AMOLED), i.e. two types of the direct addressing and the Thin Film Transistor (TFT) matrix addressing. The AMOLED comprises pixels arranged in array and belongs to active display type, which has high lighting efficiency and is generally utilized for the large scale display devices of high resolution. Because the both the thin film transistor driving the organic light emitting diode and the organic light emitting diode itself have the threshold voltage deviations. Thus, the AMOLED display device generally requires setting the compensation system for compensation.
FIG. 1 is a structure diagram of an AMOLED compensation system according to prior art, comprising a plurality of pixel units 10 aligned in array, a source drive circuit 20 electrically coupled to each pixel unit 10, a gate drive circuit 30 electrically coupled to each pixel unit 10, a detection start circuit 40 electrically coupled to each pixel unit 10, a current detector 50 electrically coupled to each pixel unit 10, a control circuit 60 electrically coupled to the source drive circuit 20, the gate drive circuit 30, the detection start circuit 40 and the current detector 50 and a storage circuit 70 electrically coupled to the control circuit 60. FIG. 2 is a circuit diagram of one pixel unit 10 in FIG. 1. The pixel unit 10 comprises a first TFT T10, a second TFT T20, a third TFT T30, a capacitor C10 and an organic light emitting diode D10. A gate of the first TFT T10 receives the gate drive signal WR provided by the gate drive circuit 30, and a source receives the data signal data provided by the source drive circuit 20; a gate of the second TFT T20 is electrically coupled to the drain of the first TFT T10, and a drain is coupled to the constant high voltage level Vdd, and a source is coupled to the node A10; a gate of the third TFT T30 receives the detection start signal RD provided by the detection start circuit 40, and a source is coupled to the node A10, and a drain is coupled to the current detector 50 through a line L; an anode of the organic light emitting diode D10 is coupled to the node A10, and a cathode is grounded; one end of the capacitor C10 is electrically coupled to the gate of the second TFT T20, and the other end is electrically coupled to the node A10.
Please refer to FIG. 1 and FIG. 2 at the same time. The working procedure of the AMOLED compensation system according to prior art comprises a TFT detection stage, an organic light emitting diode detection stage and a display stage. The TFT detection stage is: the gate drive signal WR is raised with the gate drive circuit 30 to connect the first TFT T10, and the source drive circuit 20 outputs the data signal data of high voltage level to the second TFT T20, and the second TFT T20 is connected; the detection start circuit 40 boosts the detection start signal RD, and the third TFT T30 is connected, and the current flows into the current detector 50 through the line L; the current detector 50 transmits the measured current to the control circuit 60; the control circuit 60 calculates the threshold voltage deviation value of the second TFT T20 and stores in the storage circuit 70. The organic light emitting diode detection stage is: the gate drive signal WR is raised with the gate drive circuit 30 to connect the first TFT T10, and the source drive circuit 20 outputs the data signal data of low voltage level to the second TFT T20, and the second TFT T20 is disconnected; the detection start circuit 40 boosts the detection start signal RD, and the third TFT T30 is connected, and the current detector 50 discharges the organic light emitting diode D10 through the line L; the current detector 50 transmits the measured current of this moment to the control circuit 60; the control circuit 60 calculates the threshold voltage deviation value of the organic light emitting diode D10 and stores in the storage circuit 70. In the display stage, the data signal data is inputted in the control circuit 60. The control circuit 60 compensates the data signal data according to the threshold voltage deviation value of the TFT T20 and the threshold voltage deviation value of the organic light emitting diode D10 stored in the storage circuit 70, and then to display on the AMOLED panel.
The aforesaid AMOLED compensation system, of which the compensated data signal data is outputted through the source drive circuit 20 cannot effectively compensate the 0 and 255 gray scale data signals, and cannot implement real-time measurement, real-time compensation to each pixel unit.